Toggle-lever press



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7 TOGGLELEVER PRESS Filed March 18, 1964 I 4 Sheets-Sheet 2 Fig.3

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TOGGLE-LEVER PRESS Filed March 18, 1964 4 Sheets-Sheet 5 I TK 1 u, a-casf} b-cos ac u Oct-18, 1966 RNEuBAuER ETAL 3,278,989

TOGGLE-LEVER IiRESS 4 Sheets-Sheet 4 Filed March 18, 1964 r 6 6 w r u .w im "102 e 0 M WM .J a M 1: M Mb 2 DNA United States Patent 3,27 8,989 TOGGLE-LEVER PRESS Rudolf Neubauer, Berlin-Hermsdorf, and Albert Welter,

Trier-Euren, Germany, assignors to Firma Rheinmetall G.m.b.H., Dusseldorf, Germany Filed Mar. 18, 1964, Ser. No. 352,729 Claims priority, application Germany, Oct. 25, 1963, R 36,420 4 Claims. '(Cl. 18-16) The invention relates to a toggle-lever press of the type disclosed in our Patent 3,205,551, issued September 14, 1965. Its object is the improvement of the pressure effect on the moulding to be compressed and a simplification of the ejection of the moulding.

It has already been proposed in a toggle-lever press to have rams adapted to be moved in opposite directions, and to have a system of toggle-levers connected to an upper ram and to the drive of the press, the levers being supported on columns rigidly connected to a lower ram. The end position of the upper ram is defined by a stop and after the end position has been reached the lower ram is raised. The upper ram is therefore intended to be arrested in the course of its downward movement by means of stops which are vertically adjustable to permit the selection of an optimum position.

The construction of a toggle-lever press just described has the advantage, through interception of the upper ram by means of adjustable stops, of permitting a better division of the compression pressures and paths for the upper and lower rams and one which is independent of the frictional forces in the mould. An adjustment, once it has been made, thereby results in a constant compression process. The upper and lower pressure cones occnring in the moulding overlap and form the -so-called neutral zone at the point of intersection of the two cones. Depending upon the adjusted height of the stops, this zone may be located in the centre of the moulding or be brought into another position.

The toggle-lever system mentioned is provided with connecting or coupling rods which are arranged between the joints of the toggle-lever arms and a hydraulic power cylinder. The purpose of the connecting rods is to provide the necessary large idle stroke for enabling the moulding to be ejected after manufacture and to be removed laterally. The system requires, for that purpose, a toggle-lever ratio of the individual arms which is greater than 1:1 because, although the latter provides a constructionally favourable design, the system cannot be raised by the connecting rods beyond a position in which the toggle-levers are at 60 and hence it is not possible to obtain an idle stroke of the requisite length. On the other hand, an unequal length ratio of the toggle-lever arms has the drawback that the time-travel diagram of the upper ram is of a different nature from that of the lower ram. It is desirable, however, that after completion of the idle stroke, or perhaps a little later, when the upper ram has already effected an initial compression of the charge, the pattern of movement which has taken place up to that point he stopped and that both the upper and the lower ram then move simultaneously towards one another with the same lengths of travel and in so doing cause the maximum force of the toggle-lever system to be applied uniformly on both sides or in a certain ratio to one another shortly before the final position is reached.

The toggle-lever system in the construction being discussed is actuated by a coupling rod which, because of the required idle stroke length engages the toggle-lever system from an inclined position until, just before the final position is reached and acting approximately at "ice right angles to the latter, it transmits the maximum force to the joint. Hence, in order to produce an accentuation of the amplitude of the force in this region, it is expedient and desirable that the coupling rod be brought in this region out of the inclined position approximately into the horizontal position.

Accordingly, it is the object of the present invention to provide a toggle-lever press which offers a substantially improved and more powerful pressing system.

The invention therefore envisages a toggle-lever press having unequal-length toggle-lever arms and rams adapted to be moved in opposite directions and is characterised in that, instead of the movement of the upper ram being limited by a stop for the slide thereof, hydraulically or mechanically operating means mounted in the press frame act on the path of the intermediate articulation point of the unequal-length toggle-lever arm in such manner that the articulation point is so held and guided in its path of movement that as the upper articualtion point and the lower press ram connected to it are raised the upper and lower rams move towards one another simultaneously with equal travels.

In a preferred embodiment of the invention, the means acting on the path of movement of the intermediate articulation point of the toggle-lever may consist of a holding rod pivotally mounted in the press frame substantially on the line of extension of the toggle-levers. Alternatively, the means may comprise a piston rod guided in like manner in a holding cylinder, or may comprise a holding bar having a curved path of movement and which is mounted on the press frame.

The invention also envisages a modified constructional form which is characterised in that the action of the force on the intermediate articulation point of the unequal-length toggle-lever arms is produced, without a coupling rod, by means of a horizontally-acting, preferably, hydraulically-actuated unit with, if required, as a further development, a limitation of the idle movement of the upper ram until the commencement of the action of the force of the actuating unit is controlled by the stroke cylinder or a similar driving assembly.

Furthermore, the invention is also concerned with the displaceabili-ty of such an actuating unit acting at right angles to the extended position of the toggle-lever within the limits of the shifting of the height of the togglelever articulation during its transmission of force and with the dimensioning of the individual parts for the purpose of obtaining required pressure cone effects.

Another toggle-lever press construction has already been proposed in which relative movement between the upper and lower rams is produced by a cam disc raising the toggle-lever system. In that construction, however, relative movement does not take place between the upper and lower rams in the manner proposed by the present invention, but displacement of the entire driving unit consisting of the toggle-lever, upper ram and the lower ram rigidly connected to the tie rods towards the press frame is produced. In that construction, the cam disc has no effect at all on the movements of the upper and lower rams in relation to one another, because their distance from one another is determined only by the tie rod. As the cam disc raises the entire toggle-lever system, the mould-ing disposed between the rams is also raised at the same time and the friction of the moulding in the mould is overcome, since the latter is rigidly connected to the machine frame. This, however, already initiates the ejection of the moulding and it is no longer possible to speak of a bilaterally operative and uniform pressing action. In particular, however, this process is difficult to repeat accurately and, .above all, is not adjustable except by providing new cam discs.

The construction according .to the invention differs very considerably from the foregoing in that in this construction a clear division is provided between the pressing operation and the ejection, as well as an accurately adjustable length of travel of the two rams, whereby the position of the neutral zone can always be determined with certainty.

By way of example only, embodiments of the invention will now be described more fully with reference to the accompanying drawings of which:

FIG. 1 is a vertical section of a toggle-lever press, the left-hand part of the figure showing one embodiment, and the right-hand part another embodiment,

FIGS. la-c are diagrammatic representations of the pressing operation,

FIG. 2 is a diagram of toggle-lever conditions when the toggle-lever arms are of equal length,

FIG. 3 is a diagram of toggle-lever conditions in a press embodying the invention,

FIGS. 4, 4a and 4b show the lever movements diagrammatically in detail,

FIG. 5 is a simplified view of the press rams and the toggle-levers in two difi'erent positions of the press and with dilferent movement limiting means, and,

FIG. 6 illustrates diagrammatically the movement and mode of operation of a horizontally acting hydraulic actuating uni-t for a press embodying the invention.

Referring first to FIG. 1, the press has a frame 1 in which the columns 2 are suspended so as to be displaceable longitudinally, a cross-piece 3 being mounted at the lower ends of the columns 2. The cross-piece serves as a support and mounting for a lower ram 4. Furthermore, on the columns there is mounted a slide 5 supporting an upper ram 6. The rams are powered by a hydraulic cylinder 7. To that end, piston rod 8 of cylinder 7 carries a crosshead 9 with coupling rods 10 mounted pivotally thereon and whichengage intermediate joint pins 11 at articulation point P of toggle-lever arms 12, 13, which are of different lengths. The upper arms 12 of the unequal-length arm toggle-lever system are connected .in each case by way. of the bearing pins 14 at articulation point B to the columns 2, while the lower arms 13 engage the slide 5 by way of bearing pins 15 at articulation point A. Above the lower ram 4 is a press table 16 with a mould 17, the lower opening of which is closed by the lower ram 4. The position of the rams shown in the drawing corresponds with the upper position of the toggle-levers in which the slide 5 and the upper ram are in the highest position. With the parts in that position, mould 17 is filled with an accurately weighed quantity of material in accordance with the workpiece to be obtained.

For a fuller explanation of a pressing or compression operation, reference will now be made to FIGS. 1a to 10.

In FIG. 1a is shown an upper ram 6 which has come to rest on a mould charge at I, while the lower ram 4 remains in its lowest position II owing to its own great weight. The distance I2 covered by the upper ram up to this point is the idle stroke.

FIG. 1b shows how the upper ram continues its downward movement until the slide 5 strikes against a stop 18 mounted on the press frame. The compression travel h covered by the upper ram is thereby terminated. The pressure cone produced in the mould charge is designated by the reference K Since no further movement of the upper'ram is possible because the slide 5 is now touching the stop 18 (FIG. 10), the cross-piece 3 rigidly connected to the tie rods 2 raised together with the lower ram 4 and covers the distance h producing the pressure cone K in the mould charge.

For the pressure-of the toggle-levers to take effect, the ideal condition during the compression operation would be a toggle-lever having arms of equal length. That is not practicable, howe er, because an equal-length-arm togglemediate articulation P of the toggle-lever system during the compression operation in such manner that the upper and lower rams move towards one another with equal travels, there is associated with the articulation point P a movement limiting means which may consist either of a holding rod 32 mounted so as to be longitudinally displaceable and pivotally mounted in the press frame, or

else, advantageously, of a piston rod 32'. The holding rod is articulated to joint pin 11 and is mounted so as to be longitudinally movable in an articulation cup 37 mounted for pivotal movement about point K in the press frame.

Mounted as movement limiting means on the holding 1 rod 32 is an adjusting nut M which, on the downward movement of the upper ram during the idle stroke, bears on the articulation cup 37, so that as the force continues I to act on point P, the latter moves substantially along a circular arc about the pivot point K and the point B is raised. The same process occurs when a piston rod 32 ;is

used instead of the holding rod 32. The piston rod 32 is guided by means of a piston M' in a suspended cylinder pivotally mounted in the press frame at K. (see FIG. 1,

This construction is advantageous when it isimi right). portant to support the articulation point P more resiliently.

As further movement occurs, movement in the direction of P is impressed on the point P. This movement, in accordance with the diagrammatic illustrations given in FIGS. 3 and 4, is along a path which is substantially an arc of a circle, the centre of which is the pivot point of the articulation cup 37; When the point P descends to P travel distances A1 of equal length are achieved by the two toggle-levers a and b or 12, 13. Those movements are shown in formula fashion in FIG, 4 and are illustrated separately in FIGS. 4a and 4b. Alteration of the travel or compression paths or distances within wide limits is possible by shifting the movement limiting'means for the articulation point P, i.e. by adjusting the nut M on the holding rod 32. A change in the movement patterns of the upper and lower rams can also be produced by an adjustment of the height of the pivot point K. To this end, the bearing bracket 38 is secured to the press frame 1 by means known per se, such as screws or the like, so as to be vertically .adjustable. Of course, the geometrical conditions described are not fully utilized in making this adjustment.

Another constructional form of the movement limiting and positive guiding means for the intermediate articulation point P is illustrated in FIG. 5, which shows the position of the toggle-levers in different positions of the press. In the left-hand half of FIG. 5, the levers are at the commencement of the positive guiding of the point P and in the right-hand half at the final position, i.e. when the pressing or compression operation is complete. Instead of a holding rod, a bar 40 is secured to the press frame in this case as the means for limiting the movement of the point P (joint pin 11), the bar having curved surfaces 41 at its ends. These curved surfaces likewise produce a positive guiding of the point P towards the point P (see FIG. 4b) when the intermediate articulation points. P (joint pins 11) strike against the curves 41 on the descent of the piston 8. To prevent a sliding movement, an antifriction bearing or a roller 42 may be arranged in this case of the joint pin 11.

FIG. 6 shows diagrammatically a modified form of the construction according to the invention with the force acting at right angles on the articulation point of the togglelevers, wherein the piston rod of a hydraulic cylinder 35 is operative, it being possible for the latter to be moved up and down by the stroke cylinder 7 or a similar driving assembly in such manner that the axial centre of the cyl- J inder always remains at right angles to the extended position. If desired, the driving assembly is also displaceable in the vertical direction after completion of the idle stroke, whether positively or in adaptation to a vertical adjustment of the toggle-lever as a whole. Depending on the type of press, two separate hydraulic cylinders may also be provided instead of a double acting cylinder, similarly to an opposed cylinder-type engine. The idle stroke is obtained in that the articulation P of the toggle-levers can be raised with little force by the stroke cylinder 7 without any notable horizontal movement within a range of i30 of the short toggle-lever arm, it being possible for the actuating piston of the working cylinder 35 to remain without power.

The ejection arrangement for the moulding is shown in FIG. 1.

Two tie rods 33 mounted in the slide extend slidably through the cross-piece 3 and can be coupled optionally with the latter by means of a locking device. The locking device is equipped with a locking wedge 34 which engages in a recess 36 in the tie rod 33, so that when the compression operation is terminated and the toggle-lever system is in the extended position, the slide 5 first moves upwardly with the tie rods 33 by the extent it of the idlemovement clearance or gap as it rises again and thereby likewise produces the interval h between the upper ram 6 and the moulding. The locking wedge 34 engaged in the recess in the tie rod is now raised with the crosspiece 3 and the ram 4 ejects the moulding at table level. When the moulding has then been removed to the side, the locking device is opened by means of a handle or an automatic release not shown in FIG. 1, after which the crosspiece returns to its lowest position and the mould can be recharged. The spring 42 associated with the stop nut, or the piston M, prevents too sudden a dropping of the cross-piece. In addition, a pad 43 may also be provided in order to intercept the cross-piece with a resilient action. When the slide travels downwardly, the locking wedges 34 again engage in the recesses 36 in the tie rods 33.

We claim:

1. A toggle-lever press for moulding material comprising in combination, a press table for supporting a mould containing material to be moulded, first and second rams movable towards and away from said press table, support means secured to said second ram, a mechanism for moving said first ram towards and away from said press table, a toggle-lever system with toggle arms of unequal length hinged together at articulation points, said toggle-lever system being connected between said mechanism, said first ram and said support means, and, joined to said articulation points, means for equalizing the simultaneous movement of said first and second rams, said equalizing means comprising pivotal connections on said press, ram movement equalization rods slidably mounted in said pivotal connections, and pivotal connection between said rods and said articulation points.

2. A toggle-lever press for moulding material comprising in combination, a press table for supporting a mould containing material to be moulded, first and second rams movable towards and away from said press table, support means secured to said second ram, a mechanism for moving said first ram towards and away from said press table, a toggle-lever system with toggle arms of unequal length hinged together at articulation points, said toggle-lever system being connected between said mechanism, said first ram and said support means, and, joined to said articulation points, means for equalizing the simultaneous movement of said first and second rams, said equalizing means comprising piston-cylinder assemblies pivotally mounted on said press, said assemblies having moving members pivotally connected to saidarticulation points.

3. A toggle-lever press as claimed in claim 1 and further comprising means for presetting the extent of slidable movement of said equalization rods in said pivotal connections.

4. A toggle-lever press for moulding material comprising in combination a press table for supporting a mould containing material to be moulded, first and second rams movable towards and away from said press table, support means secured to said second ram, a mechanism for moving said first ram towards and away from said press table, a toggle-lever system with toggle arms of unequal length in said system, said toggle arms being hinged together at an articulation point, pivotal connections between said system, said first ram and said support means, and, connected to said articulation point, a fluid-actuated piston-cylinder unit carried by said mechanism.

References Cited by the Examiner UNITED STATES PATENTS 2,565,522 8/1951 Renier 1830 3,015,848 1/1962 Hollfritsch 1830 3,103,701 9/1963 Calchera m1 1830XR 3,205,551 9/1965 Neubauer et al.

FOREIGN PATENTS 66,980 5/1957 France. 916,327 1/1963 Great Britain.

1'. SPENCER OVERHOLSER, Primary Examiner.

I. HOWARD FLINT, Examiner. 

4. A TOGGLE-LEVER PRESS FOR MOULDING MATERIAL COMPRISING IN A COMBINATION A PRESS TABLE FOR SUPPORTING A MOULD CONTAINING MATERIAL A PRESS TABLE FOR SUPPORTING A MOULD MOVABLE TOWARDS AND AWAY FROM SAID PRESS TABLE, SUPPORT MEANS SECURED TO SAID SECOND RAM, AMECHANISM FOR MOVING SAID FIRST RAM TOWARDS AND AWAY FROM SAID PRESS TABLE, A TOGGLE-LEVER SYSTEM WITH TOGGLE ARMS OF UNEQUAL LENGTH IN SAID SYSTEM, SAID TOGGLE ARMS BEING HINGED TOGETHER AT AN ARTICULAR POINT, PIVOTAL CONNECTIONS BETWEEN SAID SYS- 